MPICH-specific initialization of mxm.

The defaults used by MXM might not be fully appropriate for mpich.  So
we automatically initialize it to our preferred defaults unless the
user is trying to override it.
Signed-off-by: Xin Zhao <xinzhao3@illinois.edu>

src/mpid/ch3/channels/nemesis/netmod/mxm/mxm_init.c

@@ -107,6 +107,7 @@ static int _mxm_conf(void);
 #define FCNAME MPIDI_QUOTE(FUNCNAME)
 int MPID_nem_mxm_init(MPIDI_PG_t * pg_p, int pg_rank, char **bc_val_p, int *val_max_sz_p)
 {
+    int r;
     int mpi_errno = MPI_SUCCESS;
 
     MPIDI_STATE_DECL(MPID_STATE_MXM_INIT);
@@ -116,6 +117,15 @@ int MPID_nem_mxm_init(MPIDI_PG_t * pg_p, int pg_rank, char **bc_val_p, int *val_
     MPIU_Assert(sizeof(MPID_nem_mxm_vc_area) <= MPID_NEM_VC_NETMOD_AREA_LEN);
     MPIU_Assert(sizeof(MPID_nem_mxm_req_area) <= MPID_NEM_REQ_NETMOD_AREA_LEN);
 
+
+    /* mpich-specific initialization of mxm */
+    /* check if the user is not trying to override the tls setting
+     * before resetting it */
+    if (getenv("MXM_TLS") == NULL) {
+        r = MPL_putenv("MXM_TLS=rc,dc,ud");
+        MPIU_ERR_CHKANDJUMP(r, mpi_errno, MPI_ERR_OTHER, "**putenv");
+    }
+
     mpi_errno = _mxm_init(pg_rank, pg_p->size);
     if (mpi_errno)
         MPIU_ERR_POP(mpi_errno);